Cold-gas refrigerator



Feb. 19, 1957 J. w. L. KOHLER ETAL X 2,781,647

COLD-GAS REFRIGERATOR Filed Dec. .50, 1954 INVENTORS LAURENS KbHLER JACOB WILLEM ALQERT TEUNIS BLOEM' AGENT United States Pate Emmasingel, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application December 30, 1954, Serial No. 478,696 Claims priority, application Netherlands January 20, 1954 Claims. c1. 62-436) This invention relates to-cold-gas refrigerators. 'As is well-known, such machines comprise a space of low temperature and a space of high temperature, which spaces freely communicate with one another by way of a freezer, a regenerator and a cooler,the volume of each space being variable by means of one or more piston-like bodies. The piston-like body acting upon the space of low temperature comprises a cap, whilst gas in the machine which is always in the same state of aggregation performs a closed thermo-dynamic cycle. A cold-gas refrigerator is frequently also termed refrigerator operating on the reversed hot-gas motor principle. Such machines may be constructed in different ways, for example as a displacer machine, as a doubleoperating machine, as a machine having its cylinders at an angle to one another, or as a machine whose working space is united with that of a hot-gas piston motor. In cold-gas refrigerators low temperatures, for example of 80 C., may be reached in one step from room temperature, but it is also possible to obtain a cooling capacity at 200 C. in machines of eificacious construction. In view of the low temperature prevailing in the room of low temperature, it may be expected that the lubrication of the piston-like body acting upon the volume of this space will cause difliculties due to the running surface for the said body having a very low temperature. Said difiiculties are suppressed by providing the piston-like body with a cap, so that any available piston springs are always opposite a portion of the wall of the cylinder having a temperature which is not unduly low. It is then possible for the piston-like body to be lubricated in the normal way. However, a consequence of this construction is that the wall of the cylinder becomes comparatively long and may constitute the boundary of parts of the machine having quite different tasks, such as the freezer, the regenerator and the cooler.

Applicants have found that it is more particularly disadvantageous for the portion of the wall constituting the running surface for the piston and the wall of the regenerator to be manufactured in one piece.

According to the invention, the wall of the cylinder in which the piston-like body comprising a cap is adapted to reciprocate and by which the space of low temperature is bounded at least in part, comprises at least two parts located one after the other, of which one part serves as a running surface for the piston-like body and the second part is constituted by the inner boundary wall of the regenerator. I

It is now possible for the wall of the regenerator to be thermally insulated from the running surface and to choose for the two parts of the wall the material most suitable for the purpose. I g

In one embodiment of the invention, there is a third part of the wall which constitutes the boundary of the space of low temperature and which forms part of the freezer. Owing to this construction, the wall of the regenerator can be thermally insulated from a wall of the space of low temperature, which space has a very low temperature indeed but nevertheless differs in temperature from the freezer to which the regenerator is connected. j

In another embodiment of the invention, the boundary wall of the regenerator consists of non-metallic material. Use is preferably made of anon-metallic material having a coefficient of thermal conductivity lower than 0.01 caL/cm. sec. C. such as a polyamide, for example nylon. The use of the non-metallic material permits of avoiding or at least materially reducing the thermal leak through the wall of the regenerator from the hot 'side of the regenerator to its cold side.

In another embodiment of the invention, the wall of the regenerator consists of hard paper." The term hard paper is to be understood in this case to mean a fibrous mass impregnated with thermo-resistant artificial resin.

An important advantage of the construction according to the invention is that an exchangeable regenerator unit is obtained, if the filling mass of the regenerator and the outer wall thereof form a unit with the inner wall. Said regenerator units may be kept in store, so that one regenerator may readily be substituted by another.

In order that the invention may be readily carried into efiect, it will now be described, by way of example, with reference to one embodiment shown in the accompanying drawing.

The figure shows a cold-gas refrigerator of the displaced type. The machine comprises a displacer 1 and a piston 2 which are adapted to move up and down with a substantially constant phase difference.

The displacer is coupled by way of a driving-rod system 3 to a crank of a crankshaft 4, the piston also being coupled by way of a driving-rod system 5 to cranks of the crank-shaft 4. The piston 2 acts upon the volume of a space 6, which is the space of low temperature.

The piston 2 and the displacer 1 both act upon the vol- 7 of high temperature.

The displacer comprises a cap 12, so that it has a considerable height. The wall of the cylinder is constituted by three portions located one after another, viz. firstly a portion 13, located at the height of the cooler and serving as a running surface for the piston. The stroke of the machine is preferably such that the portion of the displacer in the vicinity of the piston rings never leaves this portion of the wall. The wall may be manufactured of a metal having satisfactory running properties, for example of cast iron.

Above this portion of the wall is a second portion 14 which forms part of the regenerator. This portion of the wall is manufactured of hard paper and exhibits low thermal conductivity. Thermal leak through the inner wall ofthe regenerator is thus pose the regenerator unit is contained in a housing, the freezer as well as the regenerator and the cooler being secured together by means of bolts 18.

In this embodiment the wall of the cylinder comprises three portions, but it is alternatively possible for the wall portions 14 and 15 to form a unit. In this case it is generally desirable that the portion 15 of the wall does not form part of the freezer or at least is not rigidly connected thereto.

Although the described embodiment refers to a displacer machine, the construction according to the invention is also applicable to other constructions of cold-gas refrigerators and more particularly to double-operating machines.

What is claimed is:

1. A cold-gas refrigerator comprising; a cylinder; a piston reciprocating in said cylinder; a chamber of relatively low temperature; a chamber of relatively high temperature; a freezer, a regenerator, and a cooler connected in series and communicating said chambers with each other; the volume of each space being varied by said reciprocating piston while a medium which is always in the same state of aggregation in the refrigerator performs a closed thermodynamic cycle therein; the wall of said cylinder being constituted of at least two portions abutting each other at adjacent ends and meeting at a point coextensive with the juncture of the cooler and the regenerator, one of said portions serving as a running surface for said piston and the other portion being the inner boundary wall of said regenerator.

2. A cold-gas refrigerator as set forth in claim 1 further comprising a third portion of said wall of the cylinder which bounds said chamber of relatively low temperature.

3. A cold-gas refrigerator as set forth in claim 1 wherein the inner boundary wall of said regenerator is constituted of a non-metallic material.

4. A cold-gas refrigerator as set forth in claim 1 wherein the inner boundary wall of said regenerator is constituted of hard paper.

5. A regenerator for use in a hot-gas reciprocating apparatus having an inlet and outlet aperture, and an inner wall portion constituted of a non-metallic material.

References Cited in the file of this patent UNITED STATES PATENTS 1,240,862 Lundgaard Sept. 25, 1917 

